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List:       opensuse
Subject:    [opensuse] Re: When I have downloads running, DNS fails.
From:       Linda Walsh <suse () tlinx ! org>
Date:       2014-07-11 14:09:22
Message-ID: 53BFF012.6050401 () tlinx ! org
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Carlos E. R. wrote:
>
> I consider asking the root servers myself "not polite".
>   
Well unless you speak named protocol, you'd be wasting their time.
I usually let named talk to them directly.


How else do you do a domain lookup?

You indicated some concern over having all your DNS
entries forwarded to someone else for resolution, but if you
rely on someone else looking up things for you, that's
exactly what you are doing -- forwarding all your DNS entries
to someone else to resolve for you...


> For that reason I run bind cache on my computer ;-)
> I have done that since about 1999.
>   
----
    Ahh.. but we are discussing the case where the DNS lookups
are not in an intermediate cache... ;-)

>
>   
>> So color me unconvinced.. but having your lower powered router look up
>> a DNS addr, is alot more likely to run into traffic contention problems
>> given the round trips to all the authoritative servers for each level.  
>>     
>
> My previous router, which was a cheap model supplied by the ISP, did
> this DNS service just fine. It was not a problem. Other routers I have
> used do it fine. It is just this particular brand and model which fails.
> In fact, it is the first time I see this particular issue.
>   
----
Are you comparing apples w/apples?

I.e are your different lines the same speed and capacity??

Are your computers the same now as then?  Or would they be able to
ask for traffic more quickly and possibly saturate your local line to
the exclusion of other traffic (like DNS)?

Generally, the trend has been toward higher usage, which can easily 
translate to
congestion or lower performance -- especially if you have some high-bw
progs saturating your line.

As someone else mentioned, your newer model router might have bigger
io-buffers, and might give better download performance, but worse 
interactive
performance during a download.

Until your DNS traffic is prioritized above the "ACK"s on download streams,
which many home routers have implemented  to improve throughput,
high download saturation may slow down DNS communication -- especially 
where the
resolution is done on your end (vs. always using someone else's DNS server,
maybe your ISP's or google's).

The ACKS from the DNS traffic have to compete with your download traffic,
and unless you use ingress filtering, DNS could become unresponsive due
to the download.

This effect can be worsened by DNS's defaulting to UDP as it doesn't have
tcp's auto-correction mechanisms.

also, on QOS, everything else doesn't need to set QOS.

Only the traffic you want to prioritize. 

Traffic w/o the QOS settings is placed in "the bulk" is given "normal"
"best-effort" -- so it can speed up some traffic by prioritizing some
traffic over 'bulk' (unrated).





 
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